Presentation on theme: "What do the following letters stand for?"— Presentation transcript:
1 What do the following letters stand for? S U V A THow many equations can you remember using those variables?
2 Constant acceleration Know the 5 constant acceleration equations.Understand how you can choose an equation with the unknowns givenTo be able to use them to solve problems involving constant acceleration.
3 The constant acc. equations S = displacement (m) U = initial velocity (m/s) (ms-1) V = final velocity (m/s) (ms-1) A = acceleration (m/s2) (ms-2) T = time taken (s)
8 Doing SUVAT questions For each question list the unknown values. Choose your equation.Substitute the values in.Solve to find the unknown.Questions 6-10 require more thought!You will need to set up simultaneous equations.
11 STARTER1. A parachutist jumps out of an aeroplane and accelerates uniformly at 9.8 ms-2 for ten seconds.a. How far does she travel?b. What is her final velocity?2. A car accelerates uniformly from 5 ms-1 to 20 ms-1 over a distance of 500m.a. How long does this take?b. What is the car’s acceleration?
12 Acceleration due to Gravity Know the links between speed, distance and time.To discuss vector and scalar terms.To introduce vector notation
13 Acceleration due to Gravity Famous scientist Galileo was probablythe first to look at how objects fall.He noticed that objects fallwith a constant acceleration.He also noticed that objects with adifferent mass fall with the sameacceleration.Legend has it that he tested this bydropping objects from the leaningtower of Pisa.
14 Acceleration due to Gravity The reason this is not always true on earth is due to air resistance.The theories of Galileo were tested on the moon landing mission.Moon LandingVacuum chamberAll objects, when dropped, fall towards the Earth in a vertical line with the same constant acceleration, provided that there is no air resistance.(M1 always assumes no air resistance!)
15 The Value of “g”Acceleration due to gravity is denoted by the lowercase letter “g”It varies slightly across the Earth surface varying with latitude and altitude.9.832ms-29.789ms-2
16 The Value of “g” The average value for g on Earth is 9.80665ms-2. In maths we use an approximation for the acceleration due to gravity to beg = 9.8ms-2Everywhere on Earth g = 9.8ms-2 when rounded to 2s.f.Other approximations then this will have a greater impact on our solutions.
17 Example 1 Dropping objects A stone is dropped from rest at a height 10 metres above the ground. Find the velocity just before it hits the ground.10m
18 Example 2 Objects Projected Upwards A ball is thrown vertically upwards and rises a height of 10 metres. Find the speed with which it was thrown and the time it takes to return to the original height.10ma is now negative. Think about it, if you throw something up, it will slow to a stop. At the very top v = 0ms-1
19 Example 2To find speed, use the fact the final velocity at top is v = 0.To find time, double the time it takes to reach the top of its height.10m
20 Have a go at the questions Working in small groups answer each question.When you have an answer to a question get your answer checked then collect the next question.Make sure you work as a group and everyone is happy with the solution.